1. Field of the Invention
The present invention relates to a broadcast encryption algorithm. More particularly, the present invention relates to a method capable of effectively generating an encryption key for broadcast encryption, and an apparatus using the method.
2. Description of Related Art
Generally, a broadcast encryption algorithm is applied to environments having a large number of users, and environments where performing a handshake between a server and a terminal is difficult, such as an environment which broadcasts contents. The broadcast encryption algorithm is a method of transmitting information to only users desired by a sender, among all users. The method is effectively used only when a set of users, receiving the information, randomly and dynamically changes.
When the broadcast encryption algorithm is applied to a contents service, the broadcast encryption algorithm encrypts a contents key to transmit to all terminals, except for any terminal that has lost user authority, using an encryption key group which enables all terminals except for terminals that lost user authority to decrypt the contents key. The encryption key group is previously generated by a server and provided to the terminals. In this case, header information corresponds to data which has the encrypted contents key, encrypted with the encryption key group, which enables all of the terminals except for terminals that lost user authority to decrypt the contents key. The server simultaneously transmits information about the terminal that lost the header information and the user authority.
The broadcast encryption algorithm is generally configured in a tree structure. Examples of such algorithms include a complete subtree (CS), a subset difference (SD), a HBES algorithm, a CuBES algorithm and the algorithm suggested by T. Asano. With respect to the broadcast encryption algorithm, there have been great efforts to reduce transmission overhead, storage overhead, computation overhead, and so forth.
Accordingly, a need exists for a method and apparatus for efficiently and effectively generating an encryption key for broadcast encryption using minimal overhead.